velo

Two false friends sit on this small word, and both catch people.

The first is French. Vélo is a bicycle, short for vélocipède, and it has nothing whatever to do with sailing: that root is Latin velox, swift, not velum, cloth. A French speaker reading li levis la velon will briefly picture a man lifting a bike. The Esperanto for a bicycle is biciklo.

The second is English. "Veil" really is the same Latin velum, so the etymology tempts you to use velo for the cloth over a face. Esperanto does not allow it: a veil is vualo, from French voile, and the two words have been kept deliberately apart despite the shared ancestor. It is a good demonstration of what a planned vocabulary does with a Latin word that split into two meanings on the way through the modern languages, namely take both and give each its own root.

Around it the derivations are the ones you would expect. Veli is to sail in the sense of proceeding under canvas, velŝipo is a sailing ship, velado is sailing as a sport, and a mast is masto. For sailing in the general sense of making a sea voyage, whatever the means of propulsion, the usual verb is navigi.